The inclusion of lipase in detergent compositions for improved cleaning performance is known, e.g. enhancement of removal of triglycerides containing soils and stains from fabrics. Examples are U.S. Pat. No. 4,769,173, Cornelissen et al. issued Aug. 29, 1989; U.S. Pat. No. 5,069,809, Lagerwaard et al., issued Dec. 3, 1991; PCT application WO94/03578 and HAPPI (Household & Personal Products Industry) No. 28/1991.
In U.S. Pat. No. 4,769,173 is disclosed a certain class of lipases consisting of fungal lipases ex Humicola lanuginosa together with strong bleaching agents in detergent compositions.
An example of a fungal lipase in this patent is the lipase ex Humicola lanuginosa, available from Amano under the tradename Amano-CE.
In U.S. Pat. No. 5,069,809 is disclosed the combination of strong bleaching agents with a lipase enzyme produced by cloning the gene encoding the lipase produced by Humicola lanuginosa and expressing the gene in Aspergillus oryzae as host for use in detergent compositions.
In WO 94/03578 is disclosed an enzymatic detergent composition containing 10 to 20000 LU (Lipolytic units) per gram of detergent composition of a lipase showing a substantial lipolytic activity during the main cycle of a wash process. This lipase is selected in particular on its inactivation behaviour with Diisopropyl Fluoro Phosphate (DFP).
In spite of the large number of publications on lipase enzymes only the lipase derived from Humicola lanuginosa and produced in Aspergillus oryzae as host has so far found wide-spread application as additive for fabric washing products. It is available from Novo Nordisk under the tradename Lipolase (TM). Gormsen and Malmos describe in HAPPI this enzyme with trademark "Lipolase" as being the first detergent lipase with a commercially relevant cost performance based on the use of recombinant DNA technology on an industrial scale.
In HAPPI is disclosed that Lipolase is the most effective during the drying step rather than the washing process itself. During the drying of the fabric, the conditions like water level are more favourable for lipolytic hydrolysis than during the actual wash cycle.
In order to optimize the stain removal performance of Lipolase, Novo Nordisk have made a number of variants.
As described in WO 92/05249 D96L variant of the native Humicola lanuginosa lipase improves the lard stain removal efficiency by a factor 4.4 over the wild-type lipase (enzymes compared in an amount ranging from 0.075 to 2.5 mg protein per liter).
In Research Disclosure No. 35944 published on Mar. 10, 1994, by Novo Nordisk is disclosed that the lipase variant (D96L) may be added in an amount corresponding to 0.001-100 mg (5-500.000 LU/l) lipase variant per liter of wash liquor.
However, the benefit of whiteness maintenance on fabrics using low levels of D96L variant in detergent compositions has not been previously recognized.
In addition, under dishcare conditions the use of low levels of D96L variant show a reduced spotting of reprecipitating greasy/oily soil substances on dishes, plates and the like.
SUMMARY OF THE INVENTION
We have now found that lipolytic enzyme variant D96L of native Humicola lanuginosa lipase may valuably be incorporated into detergent compositions at a level of from 50 lipolytic units (LU) to 8500 LU per liter wash solution.
The inclusion of D96L at these low levels provide a significant benefit in whiteness maintenance performance when compared to the same detergent composition but containing an identical hydrolytic activity (same amount of LU/l) of the Lipolase.TM. enzyme.
It is an object of the present invention to provide detergent compositions comprising the lipolytic variant D96L of the native lipase derived from Humicola lanuginosa at levels of from 50 LU to 8500 LU per liter wash solution. In particular the detergent composition with D96L variant is a compact detergent composition.